From the perspective of preserving the global environment, wind turbine generators using renewable energy, i.e. wind power, are becoming popular. To improve power generation efficiency, it is desired to increase the size of the wind turbine generator. Particularly, wind turbine generators installed offshore are expensive to construct in comparison to those installed onshore and thus, it is desired to improve power generation efficiency by increasing the size of the wind turbine generator so as to improve profitability.
With increased output of the generator produced by the larger wind turbine generator, heat loss from the generator increases. In the wind turbine generator in which the rotation of the rotor is transmitted to the generator by a hydraulic transmission formed by a hydraulic pump and a hydraulic motor, in addition to the heat loss from the generator, there is heat loss from the hydraulic transmission. Thus, a wind turbine generator having a function of cooling a heat-producing component such as the generator and the hydraulic transmission is desired.
In view of this, Patent Literature 1 proposes a wind turbine generator having a cooling system for cooling a converter, a transformer and a control unit. The cooling system includes a plurality of heat exchangers installed around a tower. In the heat exchangers, a cooling medium having cooled the converter, the transformer and the control unit is cooled by heat exchange with atmospheric air.
Patent Literature 2 discloses a cooling device for a wind turbine generator. The cooling device has a heat exchanger to cool a plurality of devices such as a converter, a transformer, a bearing box and a generator. Cooling water cools the devices and then is cooled by the heat exchanger installed on an outer wall of a tower and a nacelle.
In Patent Literature 3 and Patent Literature 4, disclosed are wind turbine generators in which an intake duct and an exhaust duct are formed in a nacelle for ventilating the nacelle which houses heat-producing components such as a gearbox and a generator. In such wind turbine generators, ambient air is introduced through the intake duct and exhausted from the exhaust duct so as to ventilate the nacelle, thereby preventing temperature rise in the nacelle.